The invention relates to a method and apparatus for controlling textile working systems responsive to the numbers of certain types of atoms, such as hydrogen atoms, detected in a length of an elongated fibrous strand being worked. Thus, the present invention relates to a method and apparatus useful for controlling drafting systems by sensing the traveling textile material. Prior art patents, relating generally to such a method and apparatus, are believed to be classified by the U.S. Patent Office in class 19, subclass 239.
In the manufacture of yarn and other elongated fibrous strands, it is desirable to achieve a degree of uniformity in the product throughout the length of the product so that both short range irregularities and long range drift in the product are reduced or eliminated. As a first step toward this goal, short term irregularities and long term drift in the product must be satisfactorily detected. Data concerning the uniformity of the product may then be employed to control the textile working system.
In known textile working systems, control of the product uniformity has been attempted at the drafting frame, where slivers are attenuated to promote parallelization. Of course, some rudimentary control can be achieved by periodically removing samples of the slivers, measuring and weighing the samples, calculating an average mass per unit length of the sliver, and adjusting the draft ratio of the drafting frame or other system parameter in accordance with the calculated average of the sample. Obviously, this approach provides control data only after the delay engendered by the testing process. Unless the sampled silver is of sufficient length and is reintroduced into the production line, this procedure constitutes destructive testing. Moreover, local variations in the sliver are not detected since an average mass per unit length is calculated. Thus, the procedure cannot be used for continuous control of the drafting frame or to detect periodic short term variations in the slivers, the period of which is indicative of a particular malfunction in the textile working system.
Accordingly, it is an object of the present invention to provide a method and apparatus for continuously and accurately controlling a textile working system by sensing the traveling fibrous output product of the system.
It is another object of the present invention to provide a method and apparatus for controlling a textile working system responsive to both short term and long term variations in the product.
Over the past twenty years, a large number of detector devices have been proposed for continuously sensing a traveling textile product: measurement of the photon absorption of the strand (see U.S. Pat. No. 3,305,688 to Lamparter); measurement of the dielectric constant of the strand; mechanical sensing of the strand using coacting rollers (see, for example, U.S. Pat. No. 2,891,287 to Raper); mechanical sensing of the strand using a system for detecting the resonant frequency thereof; measuring optical diffraction of continuous filaments; and, measuring the air flow resistance of the strand in a confined space.
Each of these detection techniques has certain disadvantages which compromise its utility. In the photon absorption technique the shadow of the strand is detected by a photoelectric detector. Such measurements are affected by the shape of the moving strand and the orientation of the fibers with respect to the detector. Dielectric constant methods suffer from erratic long term drifts caused primarily by variations in moisture. The accuracy of mechanical sensing by coacting rollers is limited by the precision of the constituent mechanical parts and cannot be used in high speed applications. Detection of the resonant frequency of a moving fibrous body requires that the body exhibit sufficient elasticity to resonate. Moreover, the detector and detected body should be acousticaly isolated from the rest of the textile working system. Optical diffraction methods are limited to continuous filaments where the individual filaments can be separated in a fixed pattern relationship. Finally, air flow resistance measurements suffer from inaccuracies caused by variations in the fiber surface except where continuous filaments are measured.
Accordingly, it is an object of the present invention to provide a method and apparatus for providing a device for controlling a high speed textile working system wherein the control is relatively unaffected by moisture, fiber length, the shape of the worked fibrous body or the orientation of the fibers with respect to a detector.
A known technique for sensing a fibrous strand involves the measurement of the beta particle absorption of the strand. Such a technique is illustrated in U.S. Pat. No. 2,981,986 to Neil. While the beta particle absorption detector has been shown to have good long term stability, the supposed radiation hazard associated with the beta particles has limited the use of the technique.
Accordingly, it is an object of the present invention to provide a method and apparatus for continuously and accurately sensing a traveling fibrous body produced by a textile working system, with accurate short term and long term response, and for controlling the system, without employing sources of radioactivity.
These and other objects and features of the invention will become apparent from the claims and from the following description when read in conjunction with the accompanying drawings.